A disturbance rejection and data rate trade-off in networked data flow control

摘要

The paper discusses a trade-off between the steady state disturbance rejection performance and the achievable end to end data rate of a non-linear networked data flow control system. The control system is subject to delay and saturation, caused by the interface delays and the one-directional data flow. The trade-off is derived from a requirement of global L-2-stability, in the limit where the loop delay tends to infinity. More specifically, it is proved that when the product of the steady state disturbance rejection ratio and a data flow discard rate is lower than 1/2, then the Popov inequality prevents L-2-stability to be proved. A numerical study is presented, using a networked wireless data flow controller suitable for regulation of the transmission buffer data volumes in fifth generation base stations. The numerical results support the derived trade-off and show that in the studied special case the Popov criterion provides a tight prediction of the L-2-stability limit. The numerical results also quantify the conservativeness of the asymptotic trade-off. (C) 2018 European Control Association. Published by Elsevier Ltd. All rights reserved.